A melting kettle is a large metallic container having a heating means used to melt and heat asphalt or similar substances to the temperature at which the asphalt or other substance may be applied to a work surface such as a roof. Melting kettles are equipped with submerged pump systems which circulate the asphalt through the kettle when a swing valve (called a "hot valve") on the pump system is open, and which pump the asphalt through a vertical discharge pipe when the valve is closed.
During normal use, the melting kettle is positioned with the vertical discharge pipe extending to a roof to which asphalt is to be applied. A worker stationed on the roof controls the opening and closing of the valve to stop and start the flow of asphalt to the roof. The worker uses a rope connected to the hot valve by rod linkages to control asphalt flow. To initiate flow of asphalt to the roof, the worker closes the hot valve by pulling the rope to pivot the valve seat into a closed condition. To stop asphalt flow to the roof, the worker releases tension on the rope and allows the valve seat to pivot under fluid pressure into the opened condition.
FIG. 1 shows a prior art submerged pump system and hot valve. The prior art system includes a platform 12 proportioned to cover a large opening in a melting kettle (not shown). Submerged pump 14 is mounted to and suspended from the platform 12 such that the pump 14 is inside the melting kettle during use. The pump 14 is made operable by a system of drive components collectively designated 16 and located within a housing 18 on the platform 12, and a rotor shaft (not shown) located inside a rotor shaft housing 13 which is suspended from the platform 12. An engine (not shown) is coupled to the drive components 16 and provides the energy necessary for driving the pump 14.
A series of flow lines are provided for re-circulating the molten asphalt within the kettle and for directing the molten asphalt to a work site when needed. A 90.degree. elbow pipe 20 is connected to the pump 14, and a second elbow pipe 24 is attached to an opposite end of the elbow pipe 20 by a pair of nipples 22 and a hex bolt 23.
A tee 28 having two horizontally facing openings and a vertically facing opening is attached to elbow pipe 24 by another nipple 26 at one of the tee's horizontally facing openings. A third elbow pipe 32 is attached to the tee 28 at the other horizontally extending opening in the tee 28. A vertical discharge pipe 30 is attached to the tee 28 at the vertically facing opening of the tee 28.
Another nipple 34 extends downwardly from elbow pipe 32 and connects the elbow pipe 32 to a hot valve 36. The valve 36 is comprised generally of a valve body 37 connected to and extending longitudinally from the nipple 34, an operating lever 38 pivotally attached to valve body 37 by a hinge 40, and a valve seat 42 attached to operating lever 38 such that it faces opening 44 of body 37.
A rod linkage 46 is pivotally attached to the operating lever 38, opposite from the hinge 40. The valve 36 can be closed and opened by the raising and lowering, respectively, of the rod 46. As described above, raising and lowering of the rod 46 is accomplished by the pulling and releasing of a rope 47 coupled to the rod 46 and extending to a roof (not shown) where a worker is stationed.
When the valve 36 is in the closed condition (shown in solid lines in FIG. 1), valve seat 42 prevents asphalt flow through opening 44 in the valve body 37. Hot asphalt entering the pump system via an inlet pipe (not shown) in the pump 14, thus travels through the elbows 20 and 24 and, upon reaching the tee 28, is pumped vertically into and through the vertical discharge pipe 30. When the valve 36 is opened (represented by dashed lines in FIG. 1) hot asphalt pumps through the elbows 20 and 24, through the tee 28 to the elbow 32 and then downwardly through the body 37 and out the opening 44 into the melting kettle.
When the valve 36 is moved from the closed condition (in which asphalt is delivered to the roof) to the opened condition (in which asphalt is circulated through the melting kettle), there often is asphalt inside the vertical discharge pipe 30 which has not yet reached the roof or other work area. This asphalt flows downwardly to the tee 28, through elbow 32, and into the kettle via valve opening 44.
While the hot valve and submerged pump systems of the prior art satisfactorily pump hot asphalt through melting kettles and through vertical discharge pipes, certain improvements in the characteristics of the hot valve systems are desired. For example, it is desirable to reduce the likelihood of carbon buildup in the hot valve and in the many fittings and pump lines. Moreover, back pressure on the pump and engine can occur due to the many fittings, elbow pipes, and pump lines through which the molten asphalt must be pushed by the pump. It is desirable to reduce this back pressure in order to maximize engine life. Also desirable is a reduced likelihood of head pressure upstream from the pump during circulation, particularly in the vertical discharge line, in order to alleviate the likelihood that hot asphalt will flow up through the vertical discharge pump when the valve is opened.
The hot asphalt valve of the present invention is directed to improving the above characteristics, as well as others which will become apparent below.